Communication method and apparatus

ABSTRACT

A communication method and an apparatus are provided herein. The method includes: sending, by a mobility management entity (MME), a track area update (TAU) accept message to a user equipment (UE), the TAU accept message comprising an identifier constructed from at least a resource pool identifier (pool-ID) that identifies a resource pool in a public land mobile network (PLMN), a mobility management entity identifier (MME-ID) that uniquely identifies the MME within the resource pool, and a UE temporary identifier that uniquely identifies the UE within the MME; and receiving, by the MME, a TAU complete message from the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/004,134, filed on Jan. 22, 2016, which is a continuation of U.S.patent application Ser. No. 14/049,990 filed on Oct. 9, 2013, now U.S.Pat. No. 9,288,779. which is a continuation of U.S. patent applicationSer. No. 13/849,299, filed on Mar. 22, 2013, now U.S. Pat. No.8,903,389. which is a continuation of U.S. patent application Ser. No.13/540,331, filed on Jul. 2, 2012, now U.S. Pat. No. 8,428,590 which isa continuation of U.S. patent application Ser. No. 12/691,137, filed onJan. 21, 2010, now U.S. Pat. No. 8,238,909. which is a continuation ofInternational Patent Application No. PCT/CN2008/071780, filed on Jul.28, 2008. The International Patent Application claims priority toChinese Patent No. 200710137637.5, filed on Jul. 27, 2007. All of theafore-mentioned patent applications are hereby incorporated by referencein their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to communication technologies, and inparticular, to a communication method and an apparatus.

BACKGROUND

With the development of the network, in the 3^(rd) GenerationPartnership Project (3GPP), manufacturers are researching the Long TermEvolved (LTE)/System Architecture Evolved (SAE) actively. As shown inFIG. 1 , the LTE/SAE architecture includes: (1) a Mobility ManagementEntity (MME) 11, configured to store mobility management context of aUE, for example, user identifier, mobility management state and locationinformation, to handle Non Access Stratum (NAS) signaling, and to ensuresecurity of the NAS signaling; and (2) an SAE gateway (GW), including aServing Gateway (S-GW) 121 and a Packet Data Network (PDN) GW 122, wherethe S-GW and the P-GW are two logical entities which may exist on thesame physical entity or different physical entities.

The S-GW stores the user-plane context of the UE, for example, an IPaddress and route information of the UE, and performs legal monitoringand packet data routing. The interface S11 between the S-GW and the MMEis responsible for communication between the MME and the S-GW, andexchanging mobility management information and session controlinformation of a UE.

The MME 11 works together with an Evolved-Universal Terrestrial RadioAccess Network (E-UTRAN) to implement the control-plane connectionthrough the S1-MME interface. The S-GW works together with the E-UTRANto implement the user-plane connection through the S1-U interface. TheMME 11 is connected with the 2 G/3 G Serving GPRS Supporting Node (SGSN)through an S3 interface, and serves as a mobility control-plane anchorbetween the 3G network and the SAE network of the UE. The S-GW isconnected with the 2 G/3 G SGSN through an S4 interface, and serves as amobility user-plane anchor between the 3G network and the SAE network ofthe UE.

The P-GW 122 serves as a user-plane anchor for a UE to access PDN,communicates with an external PDN through an SG1 reference point, andimplements packet routing and forwarding, policy and chargingenhancement, and packet filtering based on each user. The P-GW 122 isconnected with the S-GW 121 through an S5 or S8 interface (in the caseof roaming) to transmit the bearer control information such as bearercreation, bearer modification and bearer deletion, and to route thepacket data.

A Policy and Charging Rules Function (PCRF) 13 transmits Quality ofService (QoS) and charging policy control information to the P-GWthrough an S7 interface.

A concept of Temporary Mobile Subscriber Identifier (TMSI) is involvedboth in SAE network and Universal Mobile Telecommunications System(UMTS). In a Circuit Switched (CS) domain, the identifier is known asTMSI; in a Packet Switched (PS) domain, the identifier is known asPacket TMSI (P-TMSI). The TMSI is designed to prevent a user from beingtracked when the user's International Mobile Subscriber Identifier(IMSI) is exposed at an air interface, which may result in infringementon the user privacy. Therefore, after the user is attached to thenetwork, the SGSN or the Mobile Switching Center (MSC) allocates a TMSIor a P-TMSI to a UE. For example, the SGSN allocates a P-TMSI to the UE,and the MSC allocates a TMSI to the UE. The TMSI is unique in a LocationArea (LA) of the UE, or the P-TMSI is unique in a Routing Area (RA),where one LA may have several RAs. When the user accesses the network, aTMSI or a P-TMSI may be used as the identifier of the UE. When the userperforms downlink paging, the user may be paged by a TMSI or a P-TMSI.If the UE discovers the paging information with the UE's TMSI or P-TMSIon the paging channel, the UE initiates the access.

When the UE accesses a new core network node, if no Iu-flex concept isintroduced, the new node searches for the old node to obtain the contextof the UE according to an LA Identifier (LAI) or an RA identifier (RAD.Due to existence of the Iu-flex, the LAI and the RAI are not enough forsearching the old node. Thus, function of the TMSI or P-TMSI is furtheradopted together with LAI/RAI to determine the old node. The Iu-flexmeans that a many-to-many relation exists between access networkdevice(s) and core network device(s) on the Iu interface. For example,an RNC is connected with many SGSNs, and an SGSN may access many RNCs.Multiple SGSNs constitute a resource pool. In a resource pool, multiplecore network nodes (such as SGSN) are connected with all Radio AccessNetwork (RAN) nodes (such as RNC) in the resource pool. In thetraditional mode, however, one access network node is connected withonly one core network node.

Furthermore, in the case of lu-flex, the RAN may find the node, whichthe UE registers with, according to the information in the TMSI/P-TMSI,as detailed below.

The TMSI/P-TMSI includes 0 to 10 configurable bits which may serve as aNetwork Resource Identifier (NRI). The NRI is used to distinguishdifferent core network nodes in a resource pool. When the UE accessesthe pool for the first time, the RAN node is unable to find thecorresponding NAS node through the NAS Node Selection Function (NNSF),so the RAN node selects a proper core network node according toprinciple(s) such as load sharing. After registering with a CN node inthe resource pool, when moving in the resource pool, the UE does notchange the CN node. The principle is as follows: The core network node,which the UE registers to, allocates a TMSI or a P-TMSI to the UE, andthe TMSI or P-TMSI carries an NRI that represents the core network node.In this way, when the UE attempts to access, the UE sends an InitialDirect Transfer (DT) message to the RAN, where the message carries theTMSI or P-TMSI. The RAN node selects the previously registered corenetwork node corresponding to the NRI in the received TMSI or P-TMSI.Therefore, the UE moves within the resource pool, while the core networknode keeps unchanged. Nevertheless, when the UE moves out of theresource pool, the RAN node is unable to find the CN node withcorresponding NRI, the RAN node reselects a new core network node, andthe UE moves within the new resource pool, still with the core networknode keeping unchanged.

The prior TMSI or P-TMSI is consisted of 32 bits, including: several(generally two) bits for distinguishing PS domain and CS domain,configurable 0-10 bits for NRI (0 bit indicates no flex), several bitsfor a restart identifier, and several other bits. The bits may beallocated adaptively according to the network deployment.

For example, in a TMSI or P-TMSI, two bits are used to distinguish theTMSI and the P-TMSI, five bits are used as a restart identifier whichprevents allocating of an allocated TMSI caused by restart of the node,seven bits are used as an NRI, and the remaining 18 bits are availablefor allocating a UE identifier to each core network node.

In the conventional art, a TMSI or P-TMSI is designed in a resourcepools. As shown in FIG. 2 , the resource pools include Pool 21, Pool 22,Pool 23, Pool 24, Pool 25, and Pool 26. The NRIs of Pool 21 are 16-20;the NRIs of Pool 22 are 11-15; the NRI of Pool 23 is 1; the NRIs of Pool24 are 6-10; the NRIs of Pool 25 are 1-5; and the NRI of Pool 26 is 11.As shown in FIG. 2 , it is assumed that Pool 21, Pool 22, Pool 24, andPool 25 are partially overlapped; each resource pool includes five corenetwork nodes, where the core network nodes are distinguished withdifferent NRIs; NRI may be reused in non-adjacent pools because the NASnode selection function or the uniqueness of the TMSI of UE in thepaging area is not affected. It is assumed that a maximum of one millionusers can be attached to each core network node, there are 12 millionusers in the overlapped area of the pool, and fewer users exist in otherareas.

In this network, 20 core network nodes are enough for attaching 12million users. The NRI may have five bits (because 2⁵=32, so the NRI isavailable for identifying 32 core network nodes). The identifiersallocated independently by each node is consisted of 21 bits (because1,000,000=2²⁰, so the NRI is available for identifying two millionusers), two bits are used for distinguishing PS domain and CS domain,and the remaining 4 (32−5−21−2) bits are used for restarting.

The SAE network still involves design of Flex. Like the prior method, ina resource pool, more than one CN node (such as MME) is connected withall RAN nodes (such as eNodeB, i.e. ENB) in the resource pool. When a UEenters a resource pool initially, a RAN node selects a CN node accordingto load sharing principle. In this way, the UE is always anchored at theselected CN node when moving in the pool or accessing. Both MME and S-GWcan be connected with ENB in the SAE network, thus there are twoconcepts: MME pool and S-GW pool. Pool overlapping is also allowed inthe SAE network. In the SAE network, the MME pool or the S-GW poolincludes a complete Track Area (TA). TA is similar to LA or RA in UMTSnetwork.

FIG. 3 shows allocation of TMSI in an overlapped MME pool. In FIG. 3 ,it is assumed that the UE allocates one TA at a time. When the UEaccesses MME pool 1 for the first time (for example, the UE enters ENB1), an MME is selected from the MME Pool 1 (briefly known as MP 1).While the UE moves from ENB1 to ENB 2 or ENB3, it is not necessary tochange the MME. When the UE moves to ENB 4, because of no interfacebetween ENB 4 and the MME in the source MP 1 (ENB 4 belongs to MP 2only), it is necessary to reselect the MME in the MP 2. In FIG. 3 , ENB2 and ENB 3 belong to two MME pools. That is, ENB2 is connected witheach MME of the two pools through an interface, and ENB 3 is connectedwith each MME of the two pools through an interface. Therefore, ENB 2and

ENB 3 are the overlap part between MME pool 1 and MME pool 2. Thebenefits of the overlapping are: When the UE returns from ENB 4 to ENB3, because ENB 3 is connected with MME pool 2, it is not necessary toreselect the MME. Reselection of the MME is not required until the UEaccesses ENB 1. That is, the overlapping avoids the ping-pong effect(i.e. ping-pong relocation of the MME). Provided that there is nointerface between ENB 3 and MME pool 2, when the UE moves between ENB 3and ENB 4 back and forth, a ping-pong effect is initiated.

For the TA concept, the SAE network allows allocating more than one TAto the UE, which is different from a UTMS network, in a UTMS network,only one LA or RA can be allocated to a UE. In this way, if the UE inthe figure above registers with the pool and the allocated TA listincludes TA 1 and TA 2, no update needs to be initiated when the UEmoves between ENB 1 and ENB 2 back and forth. That is, no update needsto be initiated when the UE moves within the allocated TAs.

SUMMARY

In one embodiment, a mobility management entity (MME) is provided thatincludes a transmitter and a receiver. The transmitter sends a trackarea update (TAU) accept message to a user equipment (UE), the TAUaccept message including an identifier constructed from at least aresource pool identifier (pool-ID) that identifies a resource pool in apublic land mobile network (PLMN), a mobility management entityidentifier (MME-ID) that uniquely identifies the MME within the resourcepool, and a UE temporary identifier that uniquely identifies the UEwithin the MME. The receiver receives a TAU complete message from theUE. In addition, the identifier uniquely identifies the UE in the PLMN.

In another embodiment, a communication method is provided that includessending, by a mobility management entity (MME), a track area update(TAU) accept message to a user equipment (UE), the TAU accept messagecomprising an identifier constructed from at least a resource poolidentifier (pool-ID) that identifies a resource pool in a public landmobile network (PLMN), a mobility management entity identifier (MME-ID)that uniquely identifies the MME within the resource pool, and a UEtemporary identifier that uniquely identifies the UE within the MME; andreceiving, by the MME, a TAU complete message from the UE. In addition,the identifier uniquely identifies the UE in the PLMN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of an LTE/SAE network in the conventional art;

FIG. 2 shows how to design a TMSI/P-TMSI in a pool in the conventionalart;

FIG. 3 shows allocation of a TMSI in an overlapped MME pool in theconventional art;

FIG. 4 is a flowchart of a method for identifying a UE in an SAE networkaccording to an embodiment of the present disclosure;

FIG. 5 shows a flowchart of setting a pool-ID which is not unique in aPLMN according to an embodiment of the present disclosure;

FIG. 6 is a flowchart of reselecting an MME according to an embodimentof the present disclosure;

FIG. 7 is a flowchart of the first application instance of reallocatingan SAE-TMSI according to an embodiment of the present disclosure;

FIG. 8 is a flowchart of the second application instance of reallocatingan SAE-TMSI according to an embodiment of the present disclosure;

FIG. 9 is a flowchart of the third application instance of reallocatingan SAE-TMSI according to an embodiment of the present disclosure;

FIG. 10 is a flowchart of transmitting an SAE-TMSI according to anembodiment of the present disclosure;

FIG. 11 is a flowchart of allocating an SAE-TMSI according to anembodiment of the present disclosure;

FIG. 12 is a signaling flowchart of the method for allocating anSAE-TMSI shown in FIG. 11 ;

FIG. 13 is a flowchart of a method for receiving and transmittinginformation according to an SAE-TMSI according to an embodiment of thepresent disclosure;

FIG. 14 shows a structure of an apparatus for identifying a UE in an SAEnetwork according to an embodiment of the present disclosure; and

FIG. 15 shows a structure of an MME in an SAE network according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

The embodiments of the present disclosure are described in detail belowwith reference to accompanying drawings.

FIG. 4 is a flowchart of a method for identifying a UE in an SAE networkaccording to an embodiment of the present disclosure. As shown in FIG. 4, the method includes:

Step 401: An SAE-TMSI is received, where the SAE-TMSI is allocated to aUE accessing SAE network, and the SAE-TMSI includes at least: a pool-ID,an MME-ID, and a UE temporary identifier.

In access process, a new SAE-TMSI is allocated to the UE. Generally,allocating a new SAE-TMSI to the UE usually happens in the followingscenarios: The UE accesses the network for the first time, or the UEenters a new pool from another pool, or the UE initiates a locationupdate process and the network decides to allocate a new SAE-TMSI.

Step 402: The SAE-TMSI is used to temporarily identify the UE thataccesses the SAE network.

That is, a pool-ID, an MME-ID, and UE temporary identifier are addedinto the SAE-TMSI in an embodiment of the present disclosure. Thepool-ID is an identifier configured for the pool, and may be unique ornon-unique in a Public Land Mobile Network (PLMN). However, no duplicatepool-ID of the adjacent pool with an overlapping part is allowed. Thepreferred implementation mode is: The pool-ID set in the adjacent poolwithout an overlapping part is also unique; the MME-ID is the identifierof the MME in the pool, and is unique in the pool; the UE temporary IDis a unique identifier available from each MME for being allocated tothe UE.

Preferably, in this embodiment, a restart identifier (restart-ID) may beadded into the SAE-TMSI. That is, an SAE-TMSI includes: a pool-ID, anMME-ID, a UE temporary id, and a restart-ID. The preferred setting modeis that such IDs are added sequentially into the SAE-TMSI in the waydescribed above. The restart-ID prevents re-allocation of an identifierat restart of the MME. The restart-ID may increase or decrease accordingto the number of times of restart, and may carry a time value.

Preferably, in this embodiment, an identifier for distinguishingcommunication system types may be added into the SAE-TMSI. For example,the identifier differentiates between different systems such as UMTS andSAE. That is, an SAE-TMSI includes: pool-ID, MME-ID, a UE temporary ID,and an identifier for distinguishing UMTS and SAE, and optionally, anidentifier for differentiating between another system and the SAEsystem. The preferred setting mode is that the identifiers mentionedabove are added sequentially into the SAE-TMSI in the way describedabove. The bit(s) for PS/CS may be multiplexed for the identifier whichidentifies the UMTS system or SAE system or other system, when thenumber of bits of the SAE-TMSI is the same as that of the TMSI/P-TMSI(namely, 32 bits). For example, 00/01 represents CS, 10 represents SAE,and 11 represents PS.

Preferably, in this embodiment, a restart-ID and an identifier foridentifying the UMTS/SAE (or other system) may be added into theSAE-TMSI together. That is, an SAE-TMSI includes: a pool-ID, an MME-ID,a UE temporary id, a restart-ID, and an identifier for identifying theUMTS/SAE (or other system). The preferred setting mode is that theidentifiers mentioned above are added sequentially into the SAE-TMSI inthe way described above.

Preferably, the pool-ID may carry a PLMN-ID. That is, the pool-ID iscomposed of a Mobile Country Code (MCC), a Mobile Network Code (MNC),and an internal pool identifier of the PLMN. The length of an identifierinvolved in this embodiment is configurable according to the actualnetwork conditions. However, the design of the SAE-TMSI is not limitedto the mode disclosed above, and other appropriate design modes are alsoapplicable.

In this embodiment, a pool-ID, an MME-ID, and UE temporary id are addedinto an SAE-TMSI and optionally, an SAE-TMSI also includes a restart-IDand/or an identifier for identifying a UMTS/SAE (or other system). Themerits of using an SAE-TMSI are described below, supposing that anSAE-TMSI includes a pool-ID, an MME-ID, and a UE temporary id.

The SAE-TMSI includes a pool-ID. An MME-ID can be configured within thepool independently, regardless of the MME configuration in the adjacentpool. This is different from that in the conventional art. In theconventional art (as shown in FIG. 2 ), in the four adjacent pools, itis not allowed to allocate the same NRI. The NRI is equivalent to theMME-ID in this embodiment. Because they are in different networks (theNRI is in the UMTS, and the MME-ID is in the SAE), they have differentnames. If the same NRI is allocated, it is possible that the sameTMSI/P-TMSI is allocated to multiple UEs in the overlapping area, whichleads to confusion and failure of paging the proper UE. That is, in theconventional art, at the time of adding, modifying, or deleting an NRIconfigured by the core network node, it is necessary to consider theconditions of other adjacent pools and avoid duplicate NRIs. After theNRI of a core network node is set, it is necessary to notify other poolsso as to prevent duplicate NRIs. In other words, in the conventionalart, at the time of adding, modifying or deleting an NRI of a corenetwork node for an accessing UE in a pool, it is necessary to considerconditions of other adjacent pools and avoid duplicate NRIs. At the timeof allocating an NRI to an accessing UE, it is necessary to notify otherpools and prevent duplicate NRIs in the adjacent pools. Moreover, when amobile user accesses a network in the conventional art, it is necessaryto traverse all network resource identifiers, thus leading tocomplicated processing, a low processing speed, and low usersatisfaction.

In this embodiment, a pool-ID is configured in the pool, and the pool-IDset for the adjacent pool is different. Therefore, at the time ofadding, modifying or deleting an MME node and setting an MME-ID within apool, the MME-ID may be set in the pool independently, without the needof considering conditions of other pools as long as no duplicate MME-IDexists in this pool. That is, in this embodiment, because a pool-ID isconfigured in the pool, it is not necessary to consider theconfiguration of the adjacent pool at the time of configuring the MME inthis pool.

In this embodiment, when the UE accesses the ENB, the access requestcarries an SAE-TMSI which includes at least: a pool-ID, an MME-ID, and aUE temporary ID. After receiving the SAE-TMSI, the ENB determines,according to the pool-ID in the SAE-TMSI, which pool the UE accesses. Ifthe configuration of this pool-ID exists in the current pool, the ENBselects the corresponding MME according to the MME-ID, and selects thisMME for the UE, thus accomplishing the UE access. If the pool-ID is notconfigured in the ENB, the ENB may select a new MME directly, withouttraversing all NRIs.

For this embodiment, setting a unique pool-ID in the PLMN brings thefollowing benefits.

If no duplicate pool-ID exists in the PLMN, the SAE-TMSI is unique inthe PLMN, and the old MME may be searched out according to the SAE-TMSI.That is because, when the UE accesses a new core network entity, the newcore network entity may search out the old core network entity accordingto the pool-ID and the MME-ID in the SAE-TMSI of the UE. In theconventional art, however, a TAI needs to be considered in searching forthe old core network entity accessed by the UE. Therefore, compared withthe conventional art, this embodiment is easier to implement, and savesnetwork resources.

If the pool-ID is unique throughout the PLMN, when the UE accesses thenetwork, it is not necessary to provide the old TAI. For example, theold TAI information does not need to be carried in the NAS messages suchas Attach request and Track Area Update (TAU) request.

Nevertheless, when the UE accesses the old network, the RAN adds the oldLAI/RAI information of the UE into an initial UE message, with a view toidentifying the same TMSI/P-TMSI allocated in different location areasand letting the core network node uniquely determine the UE according tothe TMSI and the LAI. In this embodiment, therefore, it is not necessaryto add the current TAI of the UE into the initial UE message.

In other words, if the pool-ID in the SAE-TMSI is unique in the PLMN,when the UE accesses the new MME, the new MME obtains information aboutthe address of the old MME from the pool-ID and MME-ID in the SAE-TMSIof the UE; or, if the pool-ID in the SAE-TMSI is not unique in the PLMN,the information about the address of the old MME may be obtainedaccording to the old LAI of the UE alone, or according to both the oldLAI and the SAE-TMSI.

Because the SAE-TMSI in an MME is unique, when the UE attaches to thenetwork, the identification request sent by the new MME to the old MMEfor obtaining the UE IMSI does not need to carry the old TAIinformation. In the case of flex, the new MME obtains the address of theold MME through the old TAI and the SAE-TMSI (if the SAE-TMSI is uniquethroughout the PLMN, the new MME can obtain the address of the old MMEthrough the SAE-TMSI alone). If the address obtained by the new MME isnot the address of the real old MME, the new MME can forward theidentification request to the real old MME through the SAE-TMSI. In theexisting UMTS, the old RAI information needs to be carried in themessage because the UE needs to be determined according to the old RAItogether with the P-TMSI. In an SGSN, a duplicate P-TMSI may exist, butthe P-TMSI is surely unique in an RAI. That is, when the UE attaches tothe network, the new MME sends a request to the old MME to request anIMSI. Because the new MME has obtained the address of the old MMEaccording to the old TAI and/or SAE-TMSI, the identification requestsent to the old MME carries only the SAE-TMSI parameter, and does notneed to carry the old TAI any more. If the old MME is the MME previouslyregistered by the UE, the old MME retrieves the IMSI of the UE accordingto the SAE-TMSI information, and sends an identification response thatcarries the IMSI to the new MME. If the MME that receives theidentification request is not the real old MME of the UE, the MMEforwards the message to the real old MME according to the SAE-TMSI, andthe old MME retrieves the IMSI according to the SAE-TMSI and returns theIMSI to the new MME. In the existing UMTS system, however, the IMSIneeds to be determined according to the SAE-TMSI together with the TAI.

In this embodiment, the SAE-TMSI may be unique at least in the pool. Dueto the TA concept, the UE may be registered in multiple TAs or multipletypes of TAs. If the list of TAs allocated to the UE is different, theSAE-TMSI needs to be unique in the same TA in the TA list allocated tothe UE. Therefore, the preferred embodiment of the present disclosure isthat the SAE-TMSI is unique in the pool, and is unique in overlappingpools. Duplicate SAE-TMSI may exist in the overlapping part. However,other appropriate modes are also applicable, and are not detailed hereany further.

FIG. 5 shows a flowchart of setting a pool-ID which is not unique in aPLMN according to an embodiment of the present disclosure. As shown inFIG. 5 , six pools exist in an area, and one pool-ID is set for eachpool, where the pool-ID is not necessarily unique, namely, non-adjacentpools may have the same pool-ID. That is, the pool-ID of the poolsnumbered 51-55 is set to 1; the pool-ID of the pools numbered 53-56 isset to 2; the pool-ID of the pool numbered 52 is set to 3; the pool-IDof the pool numbered 54 is set to 4. In this way, the PLMN-ID may bereused in the PLMN, and the bits are saved. However, in order to preventduplicate SAE-TMSI in the overlapping part, no duplicate pool-ID can beused for overlapping pools. That is, it is acceptable that non-adjacentpools have the same SAE-TMSI. That is because the TA list allocated to aUE never crosses different pools, and it is impossible that duplicateSAE-TMSIs exist in the same area. In principle, duplicate pool-ID may beallocated to adjacent pools without any overlapping part, but such aconfiguration is not recommendable. When an idle UE moves from a pool toan adjacent pool, a TAU process is initiated. If the two pools have thesame pool-ID, it is possible that the ENB accessed by the UE selects theMME having the corresponding MME-ID in the adjacent pool directly,without triggering new MME selection. Or, when both pools have theMME-ID in the SAE-TMSI of the UE, no new MME selection is triggered.Therefore, it is preferred if the pool-ID of the pool numbered 55 is setto 5, and the pool-ID of the pool numbered 56 is set to 6, namely, if noduplicate pool-ID exists in the PLMN. In this way, new MME selection isalways initiated whenever the UE accesses other pools.

As shown in FIG. 3 and FIG. 5 , supposing that the pool-ID of MME pool 1is 1 and the pool-ID of MME pool 2 is 2, according to the technicalsolution under the embodiment of present disclosure, the UE accesses ENB1 when the UE enters pool 1 for the first time. ENB 1 discovers that thepool-ID in the SAE-TMSI of the UE is not configured or is not equal to1, and therefore, selects a new MME directly. ENB1 may select an MMEaccording to the principle(s) such as load balance. When the UE moves toENB 2 and initiates access, ENB 2 selects the old MME directly accordingto the pool-ID and the MME-ID in the SAE-TMSI. When the UE moves to ENB4, a TAU process is triggered. ENB 4 discovers that no such pool-ID isconfigured (only pool-ID=2 is configured for ENB 4), and then selects anew MME directly. At the time of changing the MME, the new MME needs toobtain information about the context or identifier of the UE. If thepool-ID of the SAE-TMSI is unique throughout the PLMN, the new MME mayobtain the address of the old MME directly according to the pool-ID andthe MME-ID in the SAE-TMSI (and optionally, MCC and MNC information,namely, PLMN information). If the pool-ID is not unique throughout thePLMN, the new MME needs to obtain the address of the old MME accordingto the old TAI of the UE. In the case of flex, the information in theSAE-TMSI needs to be considered together to determine the address of theold MME.

Besides, this scenario may occur in the network. The same pool-ID isconfigured for adjacent pools without any overlapping area. A UEinitiates TAU process when moving from a pool to an adjacent pool whichhas the same pool-ID. An initial direct transfer message is sent to theRAN (which generally refers to the ENB), and the RAN node selects an MMEaccording to the pool-ID and the MME-ID in the SAE-TMSI of the UE(supposing that the MME-ID also exists in the new pool), withouttriggering new MME selection, because a TAU request is sent to the MMEwith the same pool-ID and the same MME-ID (in fact, the MME is the MMEof the new pool rather than the old MME). Another scenario may occur: Ifthe same pool-ID is configured for adjacent or non-adjacent pools, theold SAE-TMSI is stored at the time of detaching. The UE moves to a newpool after detaching, and attaches to the pool. No new MME selection istriggered, if the pool-ID of the new pool is same as the pool-ID of thepool which UE detaches from, and if the MME-ID in the SAE-TMSI of the UEexists in the new pool. In this case, the accessed MME may be not themost appropriate MME, and it is better to trigger new MME selection.Therefore, a process of reselecting an MME is put forward to cope withthe foregoing scenario. FIG. 6 shows the detailed process. FIG. 6 is aflowchart of reselecting an MME according to an embodiment of thepresent disclosure. As shown in FIG. 6 , it is possible that the pool-IDand the MME-ID of an MME are the same as the pool-ID and the MME-ID inthe SAE-TMSI while the MME is actually different. In this case, theprocess of reselecting the MME is as follows, taking the TAU as anexample:

Step 601: The UE sends an Initial Direct Transfer message to the ENB.The Initial Direct Transfer message includes a NAS message, and the NASmessage includes a TAU request and an SAE-TMSI. Further, the TAU requestmay include a TAI.

Step 602: After receiving the Initial Direct Transfer message, the ENBselects an MME (such as MME 1) whose pool-ID and MME-ID are the same asthose carried in the SAE-TMSI.

Step 603: The ENB sends an initial UE message to MME 1. The initial UEmessage carries a TAU request.

Step 604: After receiving the TAU request, MME1 discovers that the MME 1itself is not the old MME previously accessed by the UE according to theTAI information (in the case of flex, the SAE-TMSI in the NAS may beconsidered together to determine the old MME). Therefore, the MME1 maydecide selection of a new MME, and trigger steps 605-607.

Step 605: The MME 1 feeds back a Reroute Command to the ENB.

Step 606: After receiving the Reroute Command, the ENB reselects a newMME, for example, MME 2.

Step 607: The ENB sends an Initial Direct Transfer message to MME 2.

Step 608: The remaining TAU process is performed. The remaining processis well known to those skilled in the art, and is not repeated here anyfurther.

In the attaching process or other processes initiated in thisembodiment, the following scenario may occur. The selected MME (such asMME 1) is not the old MME of the UE (the old MME may be determinedaccording to the old TAI information of the UE). The selected MME 1 maytrigger selection of a new MME (such as MME 2). Or the ENB selects a newMME (such as MME 2) directly, and forwards a Network Access Server (NAS)message to the new MME2. The selected MME 1 sends a Reroute Commandmessage to the RAN, and the RAN selects a new MME 2 and sends themessage to the new MME 2. Or, the selected MME 1 selects a new MME 2 andforwards the NAS message to the new MME 2 directly. Or, the selected MME1 selects a new MME 2 and notifies the new MME 2 information to the RAN,and the RAN initiates access to the new MME 2. The prerequisites oftriggering the new MME 2 to send a Reroute Command message or triggeringthe new MME 2 selection may be: The load of the selected MME 1 exceeds aset threshold, and is not appropriate for bearing a new UE; or theselected MME 1 discovers that the request is not a real-time-sensitiveNAS request such as TAU or Attach. If such prerequisites are notfulfilled, the new MME 2 selection is necessarily triggered.

This embodiment may avoid reselection in this way: for example, when theUE accesses the RAN, the UE not only reports the SAE-TMSI, but alsoreports the old TAI to the RAN node. When the RAN node discovers thatthe TAI does not belong to this pool, the RAN node may select a new corenetwork node. That is, the Intra Domain NAS Node Selector in the InitialDirect Transfer message sent by UE when accessing the RAN furthercarries a TAI.

Besides, in this embodiment, the IDs in the SAE-TMSI may be configuredaccording to the actual network conditions. For example, it is assumedthat one pool is set for each province, the capacity of each MME is 1million users, a pool in a province has at most six adjacent pools, anda maximum of 100 million users exist in a province. The SAE-TMSI may beset as: 21 bits are used for the UE temporary id (so each MME isavailable to at most 2 million users), 3 bits are used for the pool-ID(reusable, available to at most 8 adjacent pools), each pool needs 100MMEs (100 million users/1 million MMEs), and 7 bits are used for theMME-ID (available to at most 128 MMEs). Supposing that the SAE-TMSI has36 bits constantly (the SAE-TMSI is extensible, and it is assumed thatthe composition of the SAE-TMSI is SAE-TMSI=pool-ID+MME-ID+UE temporaryid+restart-ID), the remaining 5 bits may be used by the restart-ID.

For example, at most 20 million users exist in Beijing's network. Themaximum capacity of each MME is 2.5 million users, and each provinceneeds a unique pool-ID. Therefore, 6 bits are used for the pool-ID(available to 64 pools, which are enough if each province has a uniquepool-ID), 22 bits are used for the UE temporary id (available to 4million users), 8 MMEs exist in a pool, and 3 or 4 bits are used for theMME-ID (allowing for extension). The remaining 36−6−22−4=4 bits areavailable to the restart-ID.

The foregoing example supposes that the SAE-TMSI is constant and the IDscan be configured flexibly according to the network conditions.

Besides, in this embodiment, the SAE network reallocates an SAE-TMSI toa UE when the preset condition(s) of reallocation is (are) fulfilled.

FIG. 7 is a flowchart of the first application instance of reallocatingan SAE-TMSI according to an embodiment of the present disclosure.

The SAE-TMSI is unique in a wide scope, and may keep unchanged in a longperiod. However, for protecting privacy, the SAE-TMSI needs to changeperiodically, and the network may perform SAE-TMSI reallocation. Thepreset conditions of the reallocation may be: The reallocation istriggered after the location is updated periodically for n times, orafter the MME is changed, or after the MME is changed for n times. Forexample, a counter is designed for the MME. Once the UE accesses thenetwork or is updated, the counter increases by 1. After the counterreaches the threshold n, the SAE-TMSI is reallocated and sent to the UE,while the counter is reset, as detailed below:

Step 701: When the UE accesses the MME, the UE sends a TAU request tothe MME.

Step 702: The MME receives the TAU request, and records the number oftimes of updating through a counter. When the counter reaches athreshold, the process proceeds to step 703.

Step 703: The MME allocates a new SAE-TMSI to the UE, and resets thecounter.

Step 704: Meanwhile, the MME returns a TAU Accept message to the user.The TAU Accept message carries a new SAE-TMSI.

That is, when the counter of the MME reaches the threshold (for example,the counter increases whenever the UE accesses, the MMEs is changed orthe TAU requests is sent), the MME allocates a new SAE-TMSI, and sendsit to the UE, and then the counter is reset.

FIG. 8 is a flowchart of the second application instance of reallocatingan SAE-TMSI according to an embodiment of the present disclosure.Moreover, a timer may be set in the network. The SAE-TMSI is reallocatedupon timeout of the timer. If the UE is idle at timeout of the timer,the SAE-TMSI may be allocated at the time of the UE accessing thenetwork, or of the network paging the UE, as detailed below:

Step 801: A timer is started after the MME allocates an SAE-TMSI to theUE. When the timer reaches the preset time limit, the process proceedsto step 802.

Step 802: The MME sends paging information to the UE, namely, pages theUE.

Step 803: The UE sends a service request to the MME, requesting a newSAE-TMSI.

Step 804: The MME allocates a new SAE-TMSI to the UE, and resets thetimer.

Step 805: The MME sends an SAE-TMSI Reallocation message to the UE. Themessage carries a new SAE-TMSI.

Step 806: The UE returns an SAE-TMSI Reallocation Accept message to theMME.

In FIG. 8 , the timer is started after the MME allocates an SAE-TMSI tothe UE. The MME needs to allocate a new SAE-TMSI to the UE after timeoutof the timer, and send the new SAE-TMSI to the UE. In the example above,if the UE is idle upon timeout of the timer, the MME pages the UE, andallocates a new SAE-TMSI to the UE after the UE accesses the network. Ifthe UE is active, step 805 and step 806 are performed directly, and thenew SAE-TMSI allocated is sent to the UE, without the need of paging theUE. Alternatively, a new SAE-TMSI is allocated to the UE when the UEaccesses the network after the timer times out. The process is similarto FIG. 8 , but no paging occurs.

FIG. 9 is a flowchart of the third application instance of reallocatingan SAE-TMSI according to an embodiment of the present disclosure. The UEmaintains the timer or counter which timer or counter is similar to theone mentioned above. When the timer or counter reaches the threshold,the UE initiates an SAE-TMSI reallocation process. The process isdescribed as below.

In FIG. 9 , the UE itself determines allocation of the SAE-TMSI. Forexample, the UE sets a timer. A TAU request is sent upon timeout of thetimer, requesting the network to reallocate an SAE-TMSI. After receivingthe TAU request, the network allocates a new SAE-TMSI to the UE, andsends the SAE-TMSI to the UE, as detailed below:

Step 901: After timeout of the timer, the UE sends a TAU request to theMME, requesting to reallocate an SAE-TMSI (namely, step 902).

Step 903: The MME allocates a new SAE-TMSI to the UE, and returns theSAE-TMSI to the UE through a TAU Accept message (namely, step 904).

Step 905: The UE sends a TAU Complete message to the MME.

As regards the method of the access network identifying the SAE-TMSI,when the UE accesses the RAN in the UMTS, the RRC message sent by UEwhen accessing the RAN carries an Initial Direct Transfer message. AnIntra Domain NAS Node Selector is involved in the Initial DirectTransfer message, and may include a P-TMSI. A NAS may also be involvedin the Initial Direct Transfer message and is transmitted from the UE tothe core network directly, for example, RAU or Attach Request. The RAUrequest or the Attach Request may include a P-TMSI. Therefore, twoP-TMSIs exist in the Initial Direct Transfer message. That leads towaste of resources for the radio air interface. That is, in the UMTS,the RRC message sent by UE when accessing the RAN carries an InitialDirect Transfer message. The Initial Direct Transfer message carries anIntra Domain NAS Node Selector which may include a P-TMSI. The InitialDirect Transfer message may further carry a NAS. The NAS is transmittedfrom the UE to the core network directly, for example, RAU or AttachRequest. The RAU request or the Attach Request may include a P-TMSI.Therefore, two P-TMSIs exist in the Initial Direct Transfer message.That leads to waste of resources for the radio air interface.

Two solutions are put forward herein to cope with the waste of resourcesin the conventional art, as described below.

A method for transmitting an SAE-TMSI is provided in an embodiment ofthe present disclosure. This method is applicable to transmitting anSAE-TMSI from a UE to a core network. As shown in FIG. 10 , the methodincludes:

Step 100: A UE sends an RRC request that carries an Initial DirectTransfer message to an evolved RAN entity in an SAE network when the UEaccesses the SAE network, where the request carries an SAE-TMSI and aNAS message, and the NAS message carries no SAE-TMSI.

That is, when the UE accesses an evolved RAN entity, the UE sends an RRCrequest that carries an Initial Direct Transfer message to the evolvedRAN entity. This message carries an SAE-TMSI and a NAS message. The NASmessage (such as Attach request and TAU request) does not need to carrythe SAE-TMSI. That is because the core network obtains the SAE-TMSIthrough the initial UE message, and does not need to obtain the SAE-TMSIthrough the NAS message.

Step 101: The evolved RAN entity adds the SAE-TMSI into an initial UEmessage through an S1 interface when the evolved RAN entity establishesa signaling association with an MME through the S1 interface, andprovides the SAE-TMSI to a core network node through the initial UEmessage.

That is, the core network node obtains the SAE-TMSI through the initialUE message, but not through the NAS message, thus saving the overhead ofthe SAE-TMSI carried in the NAS message again, and reducing the resourceoverhead of the air interface and the S1 interface.

In other words, in the SAE system in this embodiment, the SAE-TMSI isincluded in the RRC part of the Initial Direct Transfer message, forexample, included in the Intra Domain NAS Node Selector. When the RANnode is further connected with the S1-MME, the SAE-TMSI is added intothe S1-AP message. In the conventional art, the initial NAS message iscarried in the RRC message and the S1-AP message, and the P-TMSI issubmitted by the UE to the core network node directly through a NASmessage. In this embodiment, however, the SAE-TMSI needs to be submittedonly once and is carried only in the RRC message rather than the NASmessage, and the UE submits the SAE-TMSI to the RAN, whereupon the RANsubmits it to the core network node through an S1-AP initial setupmessage.

As shown in FIG. 11 , another method for allocating an SAE-TMSIaccording to an embodiment of the present disclosure includes thefollowing steps:

Step 110: An SAE-TMSI for allocation is calculated. The SAE-TMSIfulfills that: A paging group calculated according to the SAE-TMSI isconsistent with a paging group calculated according to an IMSI.

Step 111: At the time of paging a UE, a paging message that carries theSAE-TMSI is sent to an evolved RAN entity, where the paging messagecarries no IMSI.

Step 112: The evolved RAN entity calculates a paging group of the UEaccording to the SAE-TMSI, and pages the UE.

That is, in this embodiment, the SAE-TMSI allocated by the MME to the UEneeds to fulfill this requirement: The paging group calculated accordingto the SAE-TMSI is consistent with the paging group calculated accordingto the IMSI under a certain algorithm. If they are consistent, when theMME delivers a paging message, the paging message sent to the RAN needsto carry only the SAE-TMSI rather than the IMSI, and the RAN calculatesthe paging group of the UE according to the SAE-TMSI, and pages the UE.

In this method, the SAE-TMSI allocated by the MME needs to fulfill thisrequirement: The paging group calculated according to the SAE-TMSI isconsistent with the paging group calculated according to the IMSI undera certain algorithm. If they are consistent, when the MME delivers apaging message according to a Discontinuous Receiving (DRX) technology,the paging message sent by the MME to the RAN needs to carry only theSAE-TMSI rather than the IMSI, and the RAN calculates the paging groupaccording to the SAE-TMSI and the calculated paging group is consistentwith the paging group calculated according to the IMSI. Therefore, it isnot necessary to deliver the IMSI to the RAN, the radio air interfaceresource is saved, and the IMSI does not need to be exposed at the RAN.

The algorithm for calculating the paging group is not limited. Forexample, modulo operation is performed. Supposing that the network needs12 paging groups, the paging group of each IMSI is calculated accordingto the (IMSI mod 12)+1. That is, the IMSI is considered as a number,which is divided by 12, and a remainder (from 0 to 11) is obtained afterthe division. The remainder “0” indicates paging group 1, the remainder1 indicates paging group 2, and so on. The algorithm given here issimple. In practice, the algorithm is not limited. The specificalgorithm is appropriate as long as the SAE-TMSI generated by thenetwork fulfills the consistency between the paging group calculatedaccording to the SAE-TMSI under the algorithm and the paging groupcalculated according to the IMSI.

As shown in FIG. 12 , the process of this embodiment includes:

1. The UE sends an Initial Direct Transfer message of an RRC message tothe ENB. The NAS message carried in the Initial Direct Transfer messageis Attach Request. In order to save resources, this NAS message does notcarry the SAE-TMSI, and only the RRC message carries the SAE-TMSI.

2. After receiving the message, the ENB selects or reselects the MMEaccording to the SAE-TMSI in the RRC. After the new MME is determined,the ENB adds the NAS message and the SAE-TMSI into initial UE message ofthe S1-AP message sent to the new MME. In this way, the new MME obtainsthe NAS message and the SAE-TMSI. That is, after receiving the InitialDirect Transfer message from the UE, the ENB sends an Initial UE messagethat carries an SAE-TMSI and an Attach request to the new MME.

3. This step is optional. The new MME may send an identification requestto the old MME. The identification request carries an SAE-TMSI (whichdoes not need to carry the old TAI), as illustrated by the dotted linein FIG. 12 .

4. The old MME returns an identification response to the new MME, asillustrated by the dotted line in FIG. 12 .

In this embodiment, other steps of the attaching process are notdetailed here any further.

A method for receiving and transmitting information according to anSAE-TMSI is provided in an embodiment of the present disclosure, asshown in FIG. 13 . In this method, the new MME sends an identificationrequest or a context request to the old MME. The identification requestor the context request does not need to carry the old TAI. The methodincludes the following detailed steps:

Step 131: If the SAE-TMSI is unique in the MME, the new MME sends anidentification request or context request that carries an SAE-TMSI to anold MME in an attaching process. The request mentioned above does notcarry the old TAI. Or the new MME sends a UE context request to an oldMME in a location update process of an MME. This request carries anSAE-TMSI, but does not carry the old TAI.

Step 132: The old MME resolves the SAE-TMSI in the request mentionedabove to obtain an address of an actual old MME if the old MME is notthe actual old MME of the UE.

An apparatus for identifying a UE in an SAE network is provided in anembodiment of the present disclosure. As shown in FIG. 14 , thestructure of the apparatus includes: a receiving unit 141 and atemporary identifying unit 142.

The receiving unit 141 is configured to receive an SAE-TMSI allocated tothe UE which accesses SAE network, where the SAE-TMSI includes at least:a pool-ID, an MME-ID, and a UE temporary identifier.

The temporary identifying unit 142 is configured to use the SAE-TMSI totemporarily identify the UE that accesses the SAE network.

The temporary identifying unit 142 includes: a determining subunit 1421,a selecting subunit 1422, and a reselecting subunit 1423 (illustrated bydotted lines in the figure).

The determining subunit 1421 is configured to: determine whether thepool-ID and the MME-ID in the SAE-TMSI carried in the access request ofthe UE are the same as those configured in the current resource pool,and, if yes, send a positive result to the selecting subunit 1422, or,if not, send a negative result to the reselecting unit 1423.

The selecting subunit 1422 is configured to select an MME for the UEaccording to the positive result.

The reselecting subunit 1423 is configured to select a new MME for theUE according to the negative result, or according to the load balanceprinciple and according to whether the pool-ID in the SAE-TMSI is uniquein the PLMN.

This apparatus may be integrated into an evolved RAN entity.

An MME in an SAE network is provided in an embodiment of the presentdisclosure. As shown in FIG. 15 , the apparatus includes: a temporaryidentifier allocating unit 151, and/or a temporary identifierreallocating unit 152.

The temporary identifier allocating unit 151 is configured to allocatean SAE-TMSI to the UE which accesses an SAE network, where the SAE-TMSIincludes at least: a pool-ID, an MME-ID, and a UE temporary identifier.

The temporary identifier reallocating unit 152 is configured toreallocate an SAE-TMSI to the UE that fulfills preset reallocationconditions. The temporary identifier reallocating unit 152 includes atleast one of following subunit: a preset threshold reallocating subunit1521, a timer reallocating subunit 1522, a location update reallocatingsubunit 1523, and a reallocating subunit 1524.

The preset threshold reallocating subunit 1521 is configured toreallocate an SAE-TMSI to the UE when the update count of the MMEreaches a preset threshold.

The timer reallocating subunit 1522 is configured to reallocate anSAE-TMSI to the UE upon timeout of the timer started after the MMEallocates the SAE-TMSI.

The location update reallocating subunit 1523 is configured toreallocate an SAE-TMSI to the UE after receiving a TAU request thatcarries the SAE-TMSI after timeout of the timer set by the UE.

The reallocating subunit 1524 is configured to send a TAU request thatcarries an SAE-TMSI or a reallocation request with an SAE-TMSI, when anupdated location recorded by a UE is received or a count in a unit oftime reaches a preset threshold, and to reallocate an SAE-TMSI to theUE.

Preferably, the temporary identifier allocating unit 151 in thisembodiment may be connected with the receiving unit 141 in FIG. 14 , andthe preset threshold reallocating subunit 1521, the timer reallocatingsubunit 1522, the location update reallocating subunit 1523, and thereallocating subunit 1524 in this embodiment may be connected with theselecting subunit 142 or the reselecting subunit 143 in FIG. 14 .

In this embodiment, therefore, different identifiers are set in theSAE-TMSI. The SAE-TMSI is added into the pool-ID in light of thefeatures of the SAE network. The TA concept employs the Multi-TARegistration mode, where multiple TAs may be allocated to each UE. Inorder to prevent duplicate SAE-TMSI in the TA, the SAE-TMSI needs to beunique in the pool. Moreover, no duplicate SAE-TMSI is acceptable inadjacent pools with an overlapping part. Therefore, with the pools beingdistinguished by the pool-ID, the SAE-TMSI is surely unique in theregistered area of the UE. The pool-ID may be unique throughout thePLMN. In this way, the SAE-TMSI is unique throughout the PLMN, and thenew MME can find the old MME through the SAE-TMSI of the UE to obtainthe UE context, without the need of considering the TAI. Therefore, theUE does not need to send the TAI. Nevertheless, the pool-ID may benon-unique in the PLMN, and a duplicate pool-ID is acceptable in thepools without any overlapping part. In order to prevent failure oftriggering selection of a new MME, it is best that the adjacent poolshave no duplicate pool-ID. This method saves the bits of the SAE-TMSI,but the new MME needs to consider the TAI in determining the old MME.

The foregoing technical solution reveals that: Different identifiers(including but not limited to: pool-ID, MME-ID, and UE temporaryidentifier) are set in the SAE-TMSI. When the UE accesses the SAEnetwork, the SAE-TMSI is allocated to the UE, and the SAE-TMSI is usedto temporarily identify the UE that accesses the SAE network. In thisembodiment, a pool-ID is configured in the SAE-TMSI, which quickens theUE update and processing when the UE accesses the SAE network,simplifies the network resource configuration for the operator, andimproves the user satisfaction. Moreover, in this embodiment, the sentmessage may carry only the SAE-TMSI rather than the old TAI, thus savingthe transmission resources.

Although the disclosure is described through some exemplary embodiments,the disclosure is not limited to such embodiments. It is apparent thatthose skilled in the art can make modifications and variations to thedisclosure without departing from the spirit and scope of thedisclosure. The disclosure is intended to cover the modifications andvariations provided that they fall in the scope of protection defined bythe following claims or their equivalents.

1. A method, comprising: sending a track area update accept message to auser equipment (UE) comprising an identity constructed from at least aresource pool-identifier, a mobility management entity identifier, and aUE temporary identifier that uniquely identifies the UE, wherein thepool-identifier identifies a resource pool in a public land mobilenetwork, the mobility management entity-identifier uniquely identifies amobility management entity within the resource pool, and the UEtemporary identifier uniquely identifies the UE within the mobilitymanagement entity; and receiving a track area update complete messagefrom the UE.
 2. The method according to claim 1, wherein thepool-identifier is unique in the public land mobile network.
 3. Themethod according to claim 1, wherein the identity is unique in thepublic land mobile network.
 4. The method according to claim 3, furthercomprising: allocating, by the mobility management entity, the identity.5. The method according to claim 1, further comprising: receiving, bythe mobility management entity, a track area update request message fromthe UE.
 6. A method comprising: receiving, by a radio access networknode, a mobility management entity pool-identifier and a mobilitymanagement entity-identifier from a user equipment (UE), wherein themobility management entity pool-identifier identifies a mobilitymanagement entity pool in a public land mobile network and the mobilitymanagement entity-identifier uniquely identifies the mobility managemententity within the mobility management entity pool; determining, by theradio access network node, that a mobility management entity identifiedby the mobility management entityidentifier and the mobility managemententity pool-identifier is associated with the radio access network node;selecting, by the radio access network node, the mobility managemententity for communication; sending, by the radio access network node, themobility management entity pool-identifier and the mobility managemententity-identifier to the mobility management entity; and receiving, bythe mobility management entity, the mobility management entitypool-identifier and the mobility management entity-identifier.
 7. Themethod according to claim 6, wherein the receiving the mobilitymanagement entity pool-identifier and the mobility managemententity-identifier comprising: receiving the mobility management entitypool-identifier and the mobility management entity-identifier through aradio resource control message.
 8. The method according to claim 7,wherein the sending the mobility management entity pool-identifier andthe mobility management entity-identifier comprising: sending themobility management entity pool-identifier and the mobility managemententity-identifier through an initial UE message.
 9. The method accordingto claim 8, wherein the initial UE message includes a track area updaterequest message.
 10. The method according to claim 8, wherein theinitial UE message includes an attach request message.
 11. A methodcomprising: receiving, by a radio access network node from a userequipment (UE), a mobility management entity pool-identifier and amobility management entity-identifier, wherein the mobility managemententity pool-identifier identifies a mobility management entity pool in apublic land mobile network and the mobility management entity-identifieruniquely identifies the mobility management entity within the mobilitymanagement entity pool; determining, by the radio access network node,that the mobility management entity identified by the mobilitymanagement entity-identifier and the mobility management entitypool-identifier is associated with the radio access network node;selecting, by the radio access network node, the mobility managemententity for communication; sending, by the radio access network node, tothe mobility management entity a system architecture evolved-temporarymobile subscriber identity comprising the mobility management entitypool-identifier, the mobility management entity-identifier and a UEtemporary identifier that uniquely identifies the UE within the mobilitymanagement entity, and wherein the TMSI system architectureevolved-temporary mobile subscriber identity identifies the UE in thepublic land mobile network; and receiving, by the mobility managemententity, the system architecture evolved-temporary mobile subscriberidentity.
 12. The method according to claim 11, wherein the systemarchitecture evolved-temporary mobile subscriber identity is unique inthe public land mobile network.
 13. The method according to claim 12,wherein the receiver is configured to receive the mobility managemententity pool-identifier and the mobility management entity-identifierthrough a radio resource control message.
 14. The method according toclaim 13, wherein the sending the system architecture evolved-temporarymobile subscriber identity comprising: sending the system architectureevolved-temporary mobile subscriber identity through an initial UEmessage.
 15. The method according to claim 14, wherein the initial UEmessage includes a track area update request message.
 16. The methodaccording to claim 14, wherein the initial UE message includes an attachrequest message.